Because the anongit URL doesn't work anymore:
exporting git://anongit.freedesktop.org/evtest (rev refs/tags/evtest-1.36) into /nix/store/nmhiz1cifr66q92xf6ccw964rdkl6qdj-evtest
Initialized empty Git repository in /nix/store/nmhiz1cifr66q92xf6ccw964rdkl6qdj-evtest/.git/
fatal: unable to connect to anongit.freedesktop.org:
anongit.freedesktop.org[0: 131.252.210.161]: errno=Connection refused
anongit.freedesktop.org[1: 2610:10:20:722:a800:0:83fc:d2a1]: errno=Network is unreachable
Replace it with the gitlab URL that is mentioned in README.md.
Fixes https://github.com/NixOS/nixpkgs/issues/475231.
Bjørn Forsman
e33bd77f16